Sparking plug.



H0 IODBL.

PATENTED SEPT. 15, 1903.

SPARKING PLUG@N APPLICATION FILED .TUER 41 M9113 m: cams varias co, Horwuwo wAsnmsYon. n. l;

UNITED STATES Patented September 15, 1903-.

PTQENT @Finca SPARKING PLUG.'

SPECIFICATION forming part of Letters Patent N 0. 738,992, dated September 15, 1903.

Application iled June 4, 1903. Serial No. 160,015. (No model.)

To {1J/Z whom it may concern:

Be it known that I, HENRY C. FOLGER, a citizen ot' the United States, residing at Somerville, county of Middlesex, State of Massachusetts, have invented an Improvement in Sparking Plugs, of which the following description, in connection with the accompanying drawings, is a specification, like letters on the drawings representing like parts.

This invention relates to the construction and insulation of a sparking plug such as used in the jump-spark-ignition systems for gasolene and other explosive engines, such as are used more particularly in automobiles.

One of the main objects of the invention is to make use of porcelain or similar substances for the insulation in such a manner that a strong and durable plug capable of. meeting all the requirements for sparking plugs of this character is produced.

The invention is more particularly defined in the appended claims.

Figure l is an exterior view of the sparking plug with the usual metallic shell removed. Fig. 2 is an end view of the sparking plug, showing the connection for the wire with the spindle of the plug; and Fig. 3 is a longitudinal section through the complete plug.

The exterior metallic shell of the sparking plu gis'of ausual andwell-knownform. It comprises a part A, exteriorly screw-threaded at a for insertion into the cylinder of the explosiveengine, and a second part B, screw-threaded into the part A for the purpose of allowing of the insertion and removal of the spindle and insulation of the plug. A shoulder c is formed upon the insulation in usual manner and the parts of the exterior shell clamp the shoulder irmly, rings or windings of asbestos or similar packing material b being placed around either side of the shoulder c. The shell of the plug is also provided with a suitable terminal a', of platinum, German silver, or similar material.

The spindle of the plug C is of usual form, having an enlarged head c2 with a terminal c of suitable material, such as platinum or German silver. The spindle is screw-threaded at cS at its opposite end, and a binding-nut E, in cooperation with the head ci, clamps the insulation in place upon the spindle. While an integral head and a binding-nut are shown for clamping against the'insulation, any equivalent means may be employed. The parts such as the head c2 and the binding-nut E, between which the insulation is clamped, Y

are herein termed the clamping ends ofthe spindle.

There is also shown herein provision for what is known as a spark-gam7 but this is a feature which may or may not be made use of in connection with the plug, as desired.

C sufficiently to receive and retain thereon a tube F of fibrous or other suitable insulating material. A screw C', forming, in effect, a continuation of the spindle C, is inserted'in the other end of the tube F in such a manner that the break f in the spindle forms a suitable gap for the purpose named.

The plug may be used either with or without the spark-gap portion,as desired. Then used without it, the conducting-wireisclamped between the nut E and a washer g. lVhen the spark-gap portion is used, a metallic connection l-I, placed under the head of the screw C, is used and the conducting-wire clamped therein in well-known manner.

The insulation for the plug consists of the porcelain core O and the inner mica tube P. By the term porcelain as used throughout the speciiication and claims, it is meant to include not only porcelain itself, but also glass and any similar fragile homogeneous material suitable for insulation purposes of this character.

The mica tube maybe formed of thin sheetmica rolled up into a tube by the aid of suitable adhesives, tubes of this character now heilig a regular article of manufacture. rlhe inclusion of substances liable to carbonization under the heat to which sparking plugs are subject should be avoided, however. The mica tube is of sufficient length to extend from the head O2 of the spindle throughout the length of and considerably beyond the IOO inclosing metallic shell, so that a double insulation exists at all points where it, would be possible for a spark to pass from the spindle C to the metallic shell A B. The mica tube is also arranged to project slightly beyond the terminal end of the porcelain core, and mica washers m are placed at the opposite end of the porcelain core, so that when the spindle is clamped in position the metallic portions of the spindle do not clamp against the porcelain core, but against mica at each end, by which means a tight and solid plug is produced without substantial danger to the porcelain by breaking. Since the mica tube does not extend entirely through the porcelain core, this result is readily obtained, and it is impossible for the spindle with its terminal head to either be screwed up into contact with the porcelain or to be forced through the porcelain .core by the explosion in the cylinder of the engine.

It is well known that porcelain has long been used in sparking plugs and that it is a good insulator, its main defect being that it is subject to breakage, which renders it useless. 'lhe construction herein described relieves the porcelain core of much of the danger of breakage occurring from shock or expansion and contraction. Mica is also well known as an excellent insulator, but unless maintained in apractically solid integral condition it is liable to short-circuit through its laminas owing to the presence of open spaces or of carbon and other conductive substances which may become lodged or forced therein. It is also exceedingly liable to disintegrate where exposed without protectionto th e action of the current or the gases from the engine.

In the construction herein employed the mica tube is thoroughly protected and remains in an integral condition. The porcelain core is also protected by the mica tube and washers as much as possible from breakage. If, however, the porcelain core should break, the mica tube would continue to afford the necessary insulation. In this manner a strong, cheap, and serviceable plug is secured capable of withstanding high-tension currents occurring in sparking plugs of this character and also capable of withstanding the severe heat to which the plug is subjected in the cylinder of a gas-engine, and also con- @serge structed in such a manner as to be perfectlygas-tight.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, is

1. A sparking plug having a central conducting-spindle provided with a terminal, an exterior conducting-shell provided with a second terminal, a double insulation separating the spindle and the shell, said insulation comprising a porcelain core and a mica tube in the core and around the spindle.

2. A sparking plug having a central conducting-spindle, formed with a spark-gap therein and provided with a terminal, an exterior conducting-shell provided with a second terminal, a double insulation separating the spindle and the shell, said insulation comprising a porcelain core and a mica tube in the core and around the spindle.

3. A sparking plug having a central conducting-spindle provided with a terminal, an exterior conducting-shell provided with a second terminal, a double insulation separating the spindle and the shell, said insulation comprising a porcelain core and a mica tube centrally seated in said core and projecting slightly therefrom at the terminal end, mica washers at the opposite ends of the core whereby the spindle when clamped in place has its clamping ends bearing against mica at both ends of the core.

4. A sparking plug having a central conductingspindle formed with a spark-gap therein and provided with a terminal, an exterior conducting-shell provided with a second terminal, a double insulation separating the spindle and the shell, said insulation comprising a porcelain core and a mica tube centrally seated in said core and projecting slightly therefrom at the terminal end, mica washers at the opposite ends of the core whereby the spindle when clamped in place has its clamping ends bearing against mica at both ends of the core.

In testimony whereof I have signed my name to this speciiication in the presence of two subscribing witnesses.

HENRY C. FOLGER.

W'itnesses:

Guo. W. GREGORY, MABEL PARTELow. 

